<?php
/**
 * YiiBase class file.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @link http://www.yiiframework.com/
 * @copyright 2008-2013 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */


/**
 * CChoiceFormat is a helper that chooses an appropriate message based on the specified number value.
 * The candidate messages are given as a string in the following format:
 * <pre>
 * 'expr1#message1|expr2#message2|expr3#message3'
 * </pre>
 * where each expression should be a valid PHP expression with <code>'n'</code> as the only variable.
 * For example, <code>'n==1'</code> and <code>'n%10==2 && n>10'</code> are both valid expressions.
 * The variable <code>'n'</code> will take the given number value, and if an expression evaluates true,
 * the corresponding message will be returned.
 *
 * For example, given the candidate messages <code>'n==1#one|n==2#two|n>2#others'</code> and
 * the number value 2, the resulting message will be <code>'two'</code>.
 *
 * For expressions like <code>'n==1'</code>, we can also use a shortcut <code>'1'</code>. So the above example
 * candidate messages can be simplified as <code>'1#one|2#two|n>2#others'</code>.
 *
 * In case the given number doesn't select any message, the last candidate message
 * will be returned.
 *
 * The PHP expressions will be evaluated using {@link evaluate}.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @package system.i18n
 */
class CChoiceFormat
{
    /**
     * Formats a message according to the specified number value.
     * @param string $messages the candidate messages in the format of 'expr1#message1|expr2#message2|expr3#message3'.
     * See {@link CChoiceFormat} for more details.
     * @param mixed $number the number value
     * @return string the selected message
     */
    public static function format($messages, $number)
    {
        $n = preg_match_all('/\s*([^#]*)\s*#([^\|]*)\|/', $messages . '|', $matches);
        if ($n === 0)
            return $messages;
        for ($i = 0; $i < $n; ++$i) {
            $expression = $matches[1][$i];
            $message = $matches[2][$i];
            if ($expression === (string)(int)$expression) {
                if ($expression == $number)
                    return $message;
            } elseif (self::evaluate(str_replace('n', '$n', $expression), $number))
                return $message;
        }
        return $message; // return the last choice
    }

    /**
     * Evaluates a PHP expression with the given number value.
     * @param string $expression the PHP expression
     * @param mixed $n the number value
     * @return boolean the expression result
     */
    protected static function evaluate($expression, $n)
    {
        return @eval("return $expression;");
    }
}